1. Field of the Invention
The invention relates to a steering apparatus for a vehicle.
2. Description of the Related Art
What is called steer-by-wire steering apparatuses are conventionally known in which a steering wheel is mechanically separated from steered wheels. For example, a steering apparatus in Japanese Patent Application Publication No. 2014-223862 (JP 2014-223862 A) has a clutch that connects and disconnects a power transmission path between the steering wheel and the steered wheels, a reaction force motor that is a source of a steering reaction force applied to the steering shaft, and a steering operation motor that is a source of a steering operation force making the steered wheels to be steered.
While a vehicle is traveling, a control apparatus for the steering apparatus makes the clutch to be released to keep the steering wheel mechanically separated from the steered wheels. The control apparatus then generates a steering reaction force through the reaction force motor and makes the steered wheels to be steered through a steering operation motor. In contrast, when the reaction force motor or the like becomes abnormal, the control apparatus makes the clutch to be engaged to keep the steering wheel mechanically coupled to the steered wheels. Consequently, the steered wheels can be steered by use of a steering torque applied by a driver.
In many of the conventional steering apparatuses including the steering apparatus in JP 2014-223862 A, when the vehicle is powered off, the clutch is engaged in view of fail safety and the like. In this case, reaction force control through the reaction force motor and steering operation control through the steering operation motor may be continuously executed after an operation of powering off the vehicle is executed and until the engagement of the clutch is completed.
Thus, when the operation of powering off the vehicle is executed during steering of the steering wheel, the following situation may occur. For example, the moment the clutch is engaged, the steering operation force generated by the steering operation motor may be transmitted to the steering wheel, causing rotation of the steering wheel unintended by a driver.